three.js/examples/js/loaders/PVRLoader.js

/*
 *	 PVR v2 (legacy) parser
 *   TODO : Add Support for PVR v3 format
 *   TODO : implement loadMipmaps option
 */

THREE.PVRLoader = function ( manager ) {

	THREE.CompressedTextureLoader.call( this, manager );

};

THREE.PVRLoader.prototype = Object.assign( Object.create( THREE.CompressedTextureLoader.prototype ), {

	constructor: THREE.PVRLoader,

	parse: function ( buffer, loadMipmaps ) {

		var headerLengthInt = 13;
		var header = new Uint32Array( buffer, 0, headerLengthInt );

		var pvrDatas = {
			buffer: buffer,
			header: header,
			loadMipmaps: loadMipmaps
		};

		if ( header[ 0 ] === 0x03525650 ) {

			// PVR v3

			return THREE.PVRLoader._parseV3( pvrDatas );

		} else if ( header[ 11 ] === 0x21525650 ) {

			// PVR v2

			return THREE.PVRLoader._parseV2( pvrDatas );

		} else {

			console.error( 'THREE.PVRLoader: Unknown PVR format.' );

		}

	}

} );

THREE.PVRLoader._parseV3 = function ( pvrDatas ) {

	var header = pvrDatas.header;
	var bpp, format;


	var metaLen = header[ 12 ],
		pixelFormat = header[ 2 ],
		height = header[ 6 ],
		width = header[ 7 ],
		// numSurfs = header[ 9 ],
		numFaces = header[ 10 ],
		numMipmaps = header[ 11 ];

	switch ( pixelFormat ) {

		case 0 : // PVRTC 2bpp RGB
			bpp = 2;
			format = THREE.RGB_PVRTC_2BPPV1_Format;
			break;

		case 1 : // PVRTC 2bpp RGBA
			bpp = 2;
			format = THREE.RGBA_PVRTC_2BPPV1_Format;
			break;

		case 2 : // PVRTC 4bpp RGB
			bpp = 4;
			format = THREE.RGB_PVRTC_4BPPV1_Format;
			break;

		case 3 : // PVRTC 4bpp RGBA
			bpp = 4;
			format = THREE.RGBA_PVRTC_4BPPV1_Format;
			break;

		default :
			console.error( 'THREE.PVRLoader: Unsupported PVR format:', pixelFormat );

	}

	pvrDatas.dataPtr = 52 + metaLen;
	pvrDatas.bpp = bpp;
	pvrDatas.format = format;
	pvrDatas.width = width;
	pvrDatas.height = height;
	pvrDatas.numSurfaces = numFaces;
	pvrDatas.numMipmaps = numMipmaps;
	pvrDatas.isCubemap 	= ( numFaces === 6 );

	return THREE.PVRLoader._extract( pvrDatas );

};

THREE.PVRLoader._parseV2 = function ( pvrDatas ) {

	var header = pvrDatas.header;

	var headerLength = header[ 0 ],
		height = header[ 1 ],
		width = header[ 2 ],
		numMipmaps = header[ 3 ],
		flags = header[ 4 ],
		// dataLength = header[ 5 ],
		// bpp =  header[ 6 ],
		// bitmaskRed = header[ 7 ],
		// bitmaskGreen = header[ 8 ],
		// bitmaskBlue = header[ 9 ],
		bitmaskAlpha = header[ 10 ],
		// pvrTag = header[ 11 ],
		numSurfs = header[ 12 ];


	var TYPE_MASK = 0xff;
	var PVRTC_2 = 24,
		PVRTC_4 = 25;

	var formatFlags = flags & TYPE_MASK;

	var bpp, format;
	var _hasAlpha = bitmaskAlpha > 0;

	if ( formatFlags === PVRTC_4 ) {

		format = _hasAlpha ? THREE.RGBA_PVRTC_4BPPV1_Format : THREE.RGB_PVRTC_4BPPV1_Format;
		bpp = 4;

	} else if ( formatFlags === PVRTC_2 ) {

		format = _hasAlpha ? THREE.RGBA_PVRTC_2BPPV1_Format : THREE.RGB_PVRTC_2BPPV1_Format;
		bpp = 2;

	} else {

		console.error( 'THREE.PVRLoader: Unknown PVR format:', formatFlags );

	}

	pvrDatas.dataPtr = headerLength;
	pvrDatas.bpp = bpp;
	pvrDatas.format = format;
	pvrDatas.width = width;
	pvrDatas.height = height;
	pvrDatas.numSurfaces = numSurfs;
	pvrDatas.numMipmaps = numMipmaps + 1;

	// guess cubemap type seems tricky in v2
	// it juste a pvr containing 6 surface (no explicit cubemap type)
	pvrDatas.isCubemap 	= ( numSurfs === 6 );

	return THREE.PVRLoader._extract( pvrDatas );

};


THREE.PVRLoader._extract = function ( pvrDatas ) {

	var pvr = {
		mipmaps: [],
		width: pvrDatas.width,
		height: pvrDatas.height,
		format: pvrDatas.format,
		mipmapCount: pvrDatas.numMipmaps,
		isCubemap: pvrDatas.isCubemap
	};

	var buffer = pvrDatas.buffer;

	var dataOffset = pvrDatas.dataPtr,
		bpp = pvrDatas.bpp,
		numSurfs = pvrDatas.numSurfaces,
		dataSize = 0,
		blockSize = 0,
		blockWidth = 0,
		blockHeight = 0,
		widthBlocks = 0,
		heightBlocks = 0;

	if ( bpp === 2 ) {

		blockWidth = 8;
		blockHeight = 4;

	} else {

		blockWidth = 4;
		blockHeight = 4;

	}

	blockSize = ( blockWidth * blockHeight ) * bpp / 8;

	pvr.mipmaps.length = pvrDatas.numMipmaps * numSurfs;

	var mipLevel = 0;

	while ( mipLevel < pvrDatas.numMipmaps ) {

		var sWidth = pvrDatas.width >> mipLevel,
			sHeight = pvrDatas.height >> mipLevel;

		widthBlocks = sWidth / blockWidth;
		heightBlocks = sHeight / blockHeight;

		// Clamp to minimum number of blocks
		if ( widthBlocks < 2 ) widthBlocks = 2;
		if ( heightBlocks < 2 ) heightBlocks = 2;

		dataSize = widthBlocks * heightBlocks * blockSize;

		for ( var surfIndex = 0; surfIndex < numSurfs; surfIndex ++ ) {

			var byteArray = new Uint8Array( buffer, dataOffset, dataSize );

			var mipmap = {
				data: byteArray,
				width: sWidth,
				height: sHeight
			};

			pvr.mipmaps[ surfIndex * pvrDatas.numMipmaps + mipLevel ] = mipmap;

			dataOffset += dataSize;

		}

		mipLevel ++;

	}

	return pvr;

};